A polycarbonate resin is generally produced using bisphenols as a monomer ingredient and by making use of its superiority such as transparency, heat resistance and mechanical strength, this resin is widely utilized as a so-called engineering plastic in the fields of electric·electronic component, automotive component, optical recording medium and optics such as lens.
The conventional polycarbonate resin is produced using a raw material derived from petroleum resources, but in recent years, depletion of petroleum resources is feared, and it is demanded to provide a polycarbonate resin using a raw material obtained from biomass resources such as plant. In addition, because of a concern that global warming due to increase or accumulation of carbon dioxide emissions may bring about climate change or the like, development of a polycarbonate resin using a plant-derived monomer as a raw material and being carbon neutral even when discarded after use is demanded. Under these circumstances, a method for obtaining a polycarbonate resin by using, as a monomer ingredient, isosorbide (hereinafter, sometimes referred to as “ISB”) that is a dihydroxy compound obtained from biomass resources, and allowing transesterification with a carbonic acid diester to proceed while removing a byproduct monohydroxy compound by distillation under reduced pressure, has been proposed (see, for example, Patent Documents 1 to 3).
A dihydroxy compound having an ether bond in the molecule, such as ISB, is generally low in the thermal stability or stability to oxygen, and a transesterification reaction of performing the reaction at a high temperature has a problem that the obtained polycarbonate resin is colored or the reaction cannot achieve a desired molecular weight. To cope with such a problem, a method of reducing a thermal load in the reaction step and thereby improving a color tone of the obtained polycarbonate resin has been reported (see, for example, Patent Document 4). Also, studies are being made on the storage method for the above-described unstable compound (see Patent Document 5) or made with the aim of enhancing the quality of the obtained polycarbonate resin by appropriately treating a mixture solution of raw materials composed of a dihydroxy compound and a carbonic acid ester (see, Patent Document 6).
Furthermore, there has been proposed a method for producing a polycarbonate resin as a copolymer of an alicyclic dihydroxy compound and an aromatic dihydroxy compound which are different in the structure of the dihydroxy compound used, wherein the dihydroxy compounds are separately dissolved (see, Patent Document 7). A relatively high temperature is required for dissolving an aromatic dihydroxy compound and therefore, an alicyclic dihydroxy compound poor in the thermal stability is, when mixed and then dissolved, disadvantageously subject to thermal deterioration, but since these compounds are dissolved separately, the alicyclic dihydroxy compound can be stored at a lower temperature and in turn, the quality of the obtained polycarbonate resin is improved.